Battery cell, battery, and electric device

Abstract

A battery cell (30), a battery (100), and an electric device. The battery cell (30) comprises a casing (31) and an electrode assembly (32). A positive electrode active material is a sodium nickel (Ni)-manganese (Mn)-iron (Fe)-based oxide, and the general chemical formula of the sodium Ni-Mn-Fe-based oxide is NaqNixMnyFezMpO2, wherein 0<q≤1, 0<x, 0<y, 0<z, 0≤p, x+y+z≥0.81, x+y+z+p≤1, and the total mass fraction of three elements, i.e., Ni, Mn and Fe, is 40-50%. In the battery cell, the lower limit of the applicable voltage is 1.5 V to 2.0 V and the upper limit of the applicable voltage is 3.7 V to 4.2 V, and the ratio of the maximum thickness of the electrode assembly (32) in a fully charged state of the battery cell (30) to the thickness of each of first walls (311) is 16-165. The technical solution can solve the problem that it is difficult to balance the swelling force and energy density of a battery, and can increase the energy density of the battery while not or less increasing the swelling force.

Description

Battery cell, battery, and electric device Cross-reference to related applications

[0001] This application claims priority to Chinese Patent Application CN202410666231.X, filed on May 27, 2024, entitled “Battery cell, battery, and electric device”, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application belongs to the technical field of batteries, and in particular relates to a battery cell, a battery, and an electric device. BACKGROUND

[0003] In the design of a battery, various performances, such as energy density, safety, swelling force, etc., need to be considered comprehensively. In order to improve the energy density of the battery, as much electrode active material as possible needs to be put into the limited battery shell. However, during the charging and discharging process of the battery, the electrode assembly often swells and transmits swelling force to the outside. If the swelling force generated by the electrode assembly to the outside is too large, it will squeeze the various components in the battery, thereby causing the performance of the battery to decrease and safety hazards to occur. Moreover, the more electrode active material put into the battery shell, the more obvious the swelling phenomenon is. Therefore, the swelling force and the energy density of the battery are often difficult to balance, which has caused certain limitations to the development of the battery. SUMMARY

[0004] In view of the above problems, the present application provides a battery cell, a battery, and an electric device, which can solve the problem that the increase of the swelling force of the battery causes safety risks and the improvement of the energy density through the design of the margin is difficult to balance, and can improve the energy density of the battery without the swelling force increasing or increasing little.

[0005] In a first aspect, the present application provides a battery cell, which comprises a shell and an electrode assembly. The shell comprises two first walls oppositely arranged along a first direction; the electrode assembly is arranged in the shell, and the electrode assembly is located between the two first walls, and the thickness direction of the electrode assembly is parallel to the first direction.

[0006] The electrode assembly comprises a positive electrode sheet, and the positive electrode sheet comprises a positive electrode active material; the positive electrode active material is a nickel-manganese-iron-based sodium-containing oxide, and the chemical general formula of the nickel-manganese-iron-based sodium-containing oxide is Na q Ni x Mn y Fe z M pO2, wherein, 0 < q < 1, 0 < x, 0 < y, 0 < z, 0 < p, x + y + z > 0.81, x + y + z + p < 1, the M comprises one or more of V, Cr, Zn, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, Ir, the total mass ratio of Ni, Mn and Fe is 40% to 50%; the lower limit of the use voltage of the battery monomer is 1.5V to 2.0V, the upper limit of the use voltage of the battery monomer is 3.7V to 4.2V, and the ratio of the maximum thickness of the electrode assembly to the thickness of the first wall under the full charge state of the battery monomer is 16 to 165.

[0007] According to the battery monomer of the embodiment of the application, the layered oxide Na q Ni x Mn y Fe z M p The c-axis cell length of Na q Ni x Mn y Fe z M p O2 as the positive electrode active material, in the charging process, Na q Ni x Mn y Fe z M p O2 occurs sodium removal reaction, and with the gradual increase of the charging voltage, or with the gradual increase of the state of charge of the battery monomer, Na q Ni x Mn y Fe z M p O2 also increases, then Na q Ni x Mn y Fe z M pThe c-axis cell length of O2 first increases and then shrinks; the cell characteristics of the positive electrode active material macroscopically show the phenomenon of first expansion and then shrinkage during the charging process, which can make the rebound rate of the positive electrode plate under full charging less than the maximum value of the rebound rate before full charging. When the lower limit of the use voltage of the battery monomer is 1.5V-2.0V and the upper limit of the use voltage of the battery monomer is 3.7V-4.2V, during the first charging process, the expansion force of the battery monomer shows a trend of first increasing and then decreasing, and the ratio of the maximum thickness of the electrode assembly under the full charging state of the battery monomer to the thickness of the first wall satisfies the above relationship. Under the premise of meeting the safety, the first wall can be designed to be thinner to improve the energy density of the battery monomer; or the thickness of the electrode assembly can be designed to be thicker, which can put as much electrode active material as possible in the shell of the battery monomer to improve the energy density of the battery monomer.

[0008] In some embodiments, the ratio of the maximum thickness of the electrode assembly under the full charging state of the battery monomer to the thickness of the first wall is 55-75.

[0009] When the ratio of the maximum thickness of the electrode assembly under the full charging state of the battery monomer to the thickness of the first wall is 55-75, the battery monomer has a higher energy density and a lower weld cracking rate of the end cover and the shell, which can balance high energy density and high reliability.

[0010] In some embodiments, the maximum thickness of the electrode assembly under the full charging state of the battery monomer is 20mm-80mm.

[0011] The maximum thickness of the electrode assembly under the full charging state of the battery monomer satisfies the above range, the electrode assembly has a smaller expansion rate, and the battery monomer has a smaller expansion force.

[0012] In some embodiments, the shell is an aluminum shell, the Young's modulus of the shell is 65Gpa-70Gpa, and the thickness of the first wall is 0.4mm-1.2mm.

[0013] In the above scheme, since the expansion force of the battery monomer under full charging is less than the maximum expansion force before full charging, the Young's modulus of the aluminum shell can be smaller, the material cost is lower, the thickness of the first wall satisfies the above range, the first wall has a higher anti-deformation ability, the thickness of the electrode assembly can be thicker and / or the thickness of the first wall can be thinner, so that the energy density of the battery monomer is higher.

[0014] In some embodiments, the thickness of the first wall is 0.4mm-0.9mm.

[0015] In some embodiments, the shell is a steel shell, the Young's modulus of the shell is 180Gpa-190GPa, and the thickness of the first wall is 0.3mm-0.9mm.

[0016] In the above scheme, since the expansion force of the battery monomer at full charge is less than the maximum expansion force before full charge, the Young's modulus of the steel shell can be smaller, the material cost is lower, the thickness of the first wall satisfies the above range, in the case that the first wall has higher deformation resistance, the thickness of the electrode assembly can be thicker and / or the thickness of the first wall is thinner, so that the energy density of the battery monomer is higher.

[0017] In some embodiments, the thickness of the first wall is 0.3mm-0.7mm.

[0018] In some embodiments, the outer shell is an aluminum plastic film, the Young's modulus of the outer shell is 70Gpa-80Gpa, and the thickness of the first wall is 100μm-300μm.

[0019] In the above scheme, since the expansion force of the battery monomer at full charge is less than the maximum expansion force before full charge, the Young's modulus of the aluminum plastic film can be smaller, the material cost is lower; the thickness of the first wall satisfies the above range, in the case that the first wall has higher deformation resistance, the thickness of the electrode assembly can be thicker and / or the thickness of the first wall can be thinner, so that the energy density of the battery monomer is higher.

[0020] In some embodiments, the outer shell is an aluminum shell, the electrode assembly includes a negative electrode tab; the battery monomer further includes a negative electrode lead-out portion, the negative electrode lead-out portion is arranged in the outer shell, and the negative electrode lead-out portion is used for electrically connecting the negative electrode tab and a conductor outside the battery monomer; the material constituting the negative electrode lead-out portion includes aluminum element, and the mass percentage of the aluminum element is greater than the mass percentage of each of other elements.

[0021] In the above scheme, sodium and aluminum do not alloy at low potential, the material of the negative electrode lead-out portion adopts aluminum, which can reduce the material cost and weight of the battery monomer compared with copper and copper-aluminum composite material.

[0022] In some embodiments, the chemical formula of the sodium-containing oxide of the nickel-manganese-iron-based satisfies 0.1≤x≤0.5. Optionally, 0.2≤x≤0.4.

[0023] In some embodiments, the chemical formula of the sodium-containing oxide of the nickel-manganese-iron-based satisfies 0.1≤y≤0.5. Optionally, 0.2≤y≤0.4.

[0024] In some embodiments, the chemical formula of the sodium-containing oxide of the nickel-manganese-iron-based satisfies 0.1≤z≤0.5.

[0025] In some embodiments, the chemical formula of the sodium-containing oxide of the nickel-manganese-iron-based satisfies 0.2≤z≤0.3.

[0026] In some embodiments, the chemical formula of the sodium-containing oxide of the nickel-manganese-iron-based satisfies 0.8≤x+y+z≤1. Optionally, 0.9≤x+y+z≤1.

[0027] In some embodiments, the electrode assembly comprises a negative electrode sheet, and the negative electrode sheet comprises a negative electrode active material, and the negative electrode active material has a porosity of 40% to 70%.

[0028] The negative electrode active material has abundant pores, which is conducive to the electrolyte to fully infiltrate through the pores, and thus the active ions in the battery cell can be effectively transmitted between the positive electrode sheet and the negative electrode sheet through the electrolyte, improving the ion transmission efficiency and improving the electrochemical performance of the battery cell. At the same time, the existence of more pores can also achieve a buffering effect in the case of volume expansion of the negative electrode active material after embedding active ions, reducing the volume expansion of the negative electrode sheet.

[0029] In some embodiments, the electrode assembly comprises a negative electrode sheet, and the negative electrode sheet comprises a negative electrode active material, and the negative electrode active material has an average pore size of 1 nm to 30 nm.

[0030] The nanopores are conducive to the electrolyte entering the inside of the negative electrode active material through capillary force, improving the electrolyte infiltration performance of the negative electrode sheet.

[0031] In some embodiments, the electrode assembly comprises a negative electrode sheet, and the negative electrode sheet comprises a negative electrode active material, and the negative electrode active material comprises hard carbon.

[0032] The hard carbon has low expansion force, and when used as a negative electrode active material, it is conducive to reducing the expansion force of the negative electrode during charging and discharging, and thus reducing the expansion force of the battery cell.

[0033] In a second aspect, the present application provides a battery, comprising a plurality of battery cells of the first aspect, and the plurality of battery cells are arranged along the first direction to form a battery cell group; the battery further comprises two end plates, and the two end plates are respectively arranged on both sides of the battery cell group in the first direction to clamp and fix the battery cell group.

[0034] According to the battery provided in the embodiments of the present application, the battery cell has high group margin, high energy density and low expansion force, and therefore the battery containing the battery cell also has the characteristics of high group margin, high energy density and low expansion force. Moreover, the battery cell has low expansion force, and therefore the top shell or the shell does not expand and deform in the full charge condition, so that the buffer structure between the battery cells can be omitted in the process of assembling the battery cells into the battery, thereby simplifying the structure of the battery and reducing the cost. The two end plates are arranged on the two sides of the battery cell group in the first direction, so as to clamp and fix the battery cell group, and protect the battery cell group in the first direction, thereby reducing the risk of damage to the battery cell group.

[0035] In some embodiments, the material of the end plate is aluminum alloy, and the Young's modulus of the end plate is 60 GPa to 70 GPa.

[0036] The material of the end plate is aluminum alloy, which is light in weight and high in strength.

[0037] In some embodiments, the thickness direction of the end plate is parallel to the first direction, and the thickness of the end plate is 20 mm to 35 mm.

[0038] The thickness of the end plate satisfies the above relationship, which can constrain the expansion deformation of the battery cell on the one hand, and occupy a smaller assembly space on the other hand, so that the battery can have a higher energy density.

[0039] In some embodiments, the battery further comprises a current collecting member, and two adjacent battery cells are connected by the current collecting member, and the current collecting member is a flat plate.

[0040] Since the battery cell provided in the present application has low expansion force, the expansion amount of the corresponding battery cell is also low, so that the buffer structure between the current collecting members of two adjacent battery cells can be omitted, and the current collecting member is a flat plate, which is simple in structure and convenient to process and manufacture.

[0041] In some embodiments, the battery further comprises a box, and the battery cell group is arranged in the box and is bonded to the bottom wall of the box.

[0042] The battery cell group is bonded to the bottom wall of the box, so as to position the battery cell group and limit the position movement of the battery cell group relative to the box.

[0043] In some embodiments, the battery further comprises a binding member, and the binding member is sleeved on the two end plates and the battery cell group, so as to fix the two end plates and the battery cell group.

[0044] The binding member is arranged, so as to fix the battery cell group.

[0045] In some embodiments, the binding member includes a first binding member, and the first binding member is a steel band or a plastic band.

[0046] The steel band has high strength and good constraint effect on the battery monomer group. The first binding member is a plastic band, and the production cost is low under the condition of meeting the binding strength.

[0047] In some embodiments, the binding member includes a first binding member, and the number of the first binding members is two, the two first binding members are arranged in a second direction, the second direction is parallel to the thickness direction of the bottom wall, and the first binding member is a plastic band.

[0048] The number of the first binding members is two, and the first binding member is a plastic band. The production cost is low under the condition of meeting the binding strength.

[0049] In some embodiments, the binding member includes a first binding member and a second binding member, the first binding member and the second binding member are arranged in a second direction, the second direction is parallel to the thickness direction of the bottom wall, the first binding member is away from the bottom wall relative to the second binding member, and the strength of the first binding member is greater than that of the second binding member.

[0050] When the first binding member and the second binding member are arranged in the second direction, the strength of the second binding member can be less than that of the first binding member due to the adhesion of the battery monomer group to the bottom wall of the box, and the second binding member and the first binding member can be made of different materials, thereby reducing the production cost.

[0051] In some embodiments, the first binding member is a steel band, and the second binding member is a plastic band.

[0052] The steel band has good strength and good constraint effect on the battery monomer group. Under the premise of meeting the binding requirement, the second binding member is a plastic band, which can reduce the cost.

[0053] In a third aspect, the application also provides a power consumption device including the battery monomer of the first aspect or the battery of the second aspect.

[0054] The battery of the embodiments of the application can be used in a power consumption device using a battery as a power source or various energy storage systems using a battery as an energy storage element to provide electric energy. The above battery has the advantages of high group margin, high energy density and low expansion force, so that when the battery is applied to various power consumption devices, it can provide strong power for the power consumption devices and improve the safety of the power consumption devices, which is conducive to improving the use experience of various power consumption devices. BRIEF DESCRIPTION OF DRAWINGS

[0055] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0056] Figure 1 is a schematic diagram of the structure of a vehicle according to one embodiment of this application;

[0057] Figure 2 is a schematic diagram of a battery according to an embodiment of this application;

[0058] Figure 3 is an exploded view of a battery cell according to an embodiment of this application;

[0059] Figure 4 is a cross-sectional view of a battery cell according to an embodiment of this application;

[0060] Figure 5 shows Na in one embodiment of this application. q Ni x Mn y Fe z M p The relationship curve between the c-axis unit cell length of O2 and the Na content;

[0061] Figure 6 shows Na in one embodiment of this application. q Ni x Mn y Fe z M p Schematic diagram of the changes in the unit cell structure during the O2 desodiumization process;

[0062] Figure 7 is a partial structural schematic diagram of a battery according to an embodiment of this application;

[0063] Figure 8 is a partial structural schematic diagram of a battery according to another embodiment of this application;

[0064] Figure 9 shows the variation curves of expansion force and voltage of the sodium secondary battery cell in Example 1 of this application under the first cycle in the voltage range of 2.0 to 3.95V;

[0065] Figure 10 shows the expansion force variation curves of the sodium secondary battery cell in Example 1 of this application during charge-discharge cycles in the voltage ranges of 1.5V to 3.65V and 1.5V to 4.0V.

[0066] The accompanying drawings are not drawn to scale.

[0067] Marking Explanation: 100-Battery; 11-Battery Cell Pack; 20-Casing; 21-First Sub-Casing; 22-Second Sub-Casing; 23-Bottom Wall; 30-Battery Cell; 31-Casing; 311-First Wall; 312-Casing; 313-End Cap; 314-Second Wall; 315-Third Wall; 32-Electrode Assembly; 321-Negative Electrode Tab; 33-Electrode Terminal; 34-Adapter; 35-Negative Lead-Out; 40-End Plate; 50-Binding Member; 51-First Binding Member; 52-Second Binding Member; 60-Buffer Component; 200-Controller; 300-Motor; 1000-Vehicle; X-First Direction; Y-Length Direction of Battery Cell; Z-Second Direction. Detailed Implementation

[0068] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0069] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0070] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0071] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0072] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0073] In the description of the embodiments of this application, the term "at least one" refers to one or more, and "more than one" refers to two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0074] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0075] The mass of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the masses of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass mentioned in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0076] To improve battery energy density, as much electrode active material as possible needs to be placed within the limited space of the battery casing. However, during battery charging and discharging, the insertion or extraction of active metal ions in the electrode active material causes its volume to expand, leading to electrode rebound and increasing the size of the electrode assembly (bare cell), thus transmitting expansion forces externally. Excessive expansion forces generated by the bare cell can compress various components within the battery, resulting in decreased battery performance and potential safety hazards.

[0077] In battery cell design, sufficient clearance, known as a group margin, is typically required between the bare cell and the casing. This margin allows for expansion of the bare cell, mitigating its negative impacts. A smaller group margin results in a larger gap between the cell and the casing, while a larger margin results in a smaller gap. While a small group margin effectively reduces the risks associated with cell expansion and facilitates casing, excessive space reduces the amount of electrode active material per unit mass or volume, leading to lower energy density. Conversely, a high group margin achieves high energy density, but the reduced internal space makes the battery more susceptible to expansion during charging, generating excessive expansion forces that cause the battery to bulge, ultimately affecting performance and reliability. Therefore, balancing battery expansion force and energy density is often difficult.

[0078] To improve the energy density of the battery while minimizing its expansion force and reducing the expansion force experienced during charging and discharging, thus mitigating structural damage, this application provides a battery cell comprising a casing and an electrode assembly. The casing includes two first walls disposed opposite each other along a first direction. The electrode assembly is disposed within the casing, located between the two first walls, with its thickness direction parallel to the first direction. The electrode assembly includes a positive electrode sheet containing a positive active material; the positive active material is a nickel-manganese-iron-based sodium oxide with the general chemical formula Na. q Ni x Mn y Fe z M p O2, wherein 0 < q ≤ 1, 0 < x, 0 < y, 0 < z, 0 ≤ p, x + y + z ≥ 0.81, x + y + z + p ≤ 1, and M includes one or more of V, Cr, Zn, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, and Ir, with the total mass percentage of Ni, Mn, and Fe being 40% to 50%. Under full charge conditions, the cell length of the positive electrode active material in at least one crystal axis direction is less than the maximum cell length in that direction before full charge. The lower limit of the operating voltage of the battery cell is 1.5V to 2.0V, and the upper limit of the operating voltage of the battery cell is 3.7V to 4.2V. The ratio of the maximum thickness of the electrode assembly to the thickness of the first wall under full charge conditions is 16 to 165.

[0079] In this battery cell, based on the cellular characteristics of the positive electrode active material, the rebound rate of the positive electrode sheet under full charge is less than the maximum rebound rate before full charge. During a single charge, the expansion force of the battery cell shows a trend of first increasing and then decreasing. The ratio of the maximum thickness of the electrode assembly to the thickness of the first wall in the fully charged state of the battery cell satisfies the above relationship. Under the premise of meeting safety requirements, the first wall can be designed to be thinner to improve the energy density of the battery cell; or, the thickness of the electrode assembly can be designed to be thicker, so that as much electrode active material as possible can be placed inside the casing of the battery cell to improve the energy density of the battery cell.

[0080] The battery cell with high energy density and low expansion force provided in this application embodiment can be assembled into a battery, and can be further applied to the manufacture of various electrical devices.

[0081] The present application is further illustrated below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0082] This application provides an electrical device that includes a battery cell or a battery.

[0083] The battery in this application embodiment can be used in electrical devices that use batteries as a power source, or in various energy storage systems that use batteries as energy storage elements, to provide electrical energy. The battery described above has the advantages of high capacity margin, high energy density, and low expansion force. Therefore, applying this battery to various electrical devices can provide strong power to the devices, improve their safety, and enhance the user experience of various electrical devices.

[0084] Electrical devices can include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0085] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device according to an embodiment of this application.

[0086] Figure 1 is a schematic diagram of the structure of a vehicle as an example. The vehicle 1000 can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0087] The vehicle 1000 has a battery 100 installed inside it. The battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000. For example, the battery 100 can be used as the operating power source for the vehicle 1000's electrical system, such as to meet the power requirements for starting, navigation, and operation of the vehicle 1000.

[0088] The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, for the power needs of the vehicle 1000 during startup, navigation and driving.

[0089] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0090] Please refer to Figure 2, which is a schematic diagram of a battery according to an embodiment of this application. The battery 100 includes a housing 20 and a battery cell 30, with the battery cell 30 housed within the housing 20. The housing 20 provides a space for the battery cell 30 and can have various structures. In some embodiments, the housing 20 may include a first sub-housing 21 and a second sub-housing 22, which overlap each other, jointly defining a space for accommodating the battery cell 30. The second sub-housing 22 may be a hollow structure with one open end, while the first sub-housing 21 may be a plate-like structure, covering the open side of the second sub-housing 22 so that the first sub-housing 21 and the second sub-housing 22 jointly define the space. Alternatively, both the first sub-housing 21 and the second sub-housing 22 may be hollow structures with one open side, with the open side of the first sub-housing 21 covering the open side of the second sub-housing 22.

[0091] In the battery 100, the battery 100 includes a plurality of battery cells 30, which can be connected in series, in parallel, or in a mixed manner. A mixed manner means that some of the battery cells 30 are connected in series and in parallel. The battery 100 may also include other structures, for example, the battery 100 may also include a busbar component for realizing the electrical connection between the plurality of battery cells 30.

[0092] Please refer to Figures 3 and 4. Figure 3 is an exploded view of a battery cell according to an embodiment of this application, and Figure 4 is a cross-sectional view of a battery cell according to an embodiment of this application. A first aspect of this application provides a battery cell 30, which includes a housing 31 and an electrode assembly 32. The housing 31 includes two first walls 311 disposed opposite each other along a first direction X. The electrode assembly 32 is disposed within the housing 31, located between the two first walls 311, and its thickness direction is parallel to the first direction X. The electrode assembly 32 includes a positive electrode sheet containing a positive active material. When the battery cell 30 is fully charged, the cell length of the positive active material in at least one crystal axis direction is less than the maximum cell length in that direction before full charging.

[0093] Among them, the battery cell 30, also known as the battery cell, is the most basic unit of the battery. A "battery cell" can be a fresh battery cell or a battery cell that has been recycled. The battery cell 30 in this application can be called a sodium secondary battery cell.

[0094] "Fully charged" means that the state of charge of a single battery cell reaches 100% or is charged to the highest cutoff voltage of a sodium secondary battery cell.

[0095] "Before reaching full charge" means that the state of charge of a single battery cell has not reached 100% or has not been charged to the highest cutoff voltage of the sodium secondary battery cell.

[0096] "One charging process" refers to the charging process of a single battery cell from any low state of charge to full charge, which can be the charging process from 0% SOC to 100% SOC.

[0097] "Cell size" refers to the cell length along the crystal axis. It is the distance from a given atom to the same atom at the same position and direction in an adjacent cell. It is an important lattice parameter (lattice parameters usually include the cell length along the three crystal axis directions a, b, and c, and the angle between the three crystal axes).

[0098] In one embodiment of this application, when the battery cell 30 is fully charged, the cell length in the c-axis direction of the positive electrode active material is less than the maximum cell length in that direction before the battery cell 30 reaches full charge.

[0099] Specifically, the positive electrode active material can be selected as a nickel-manganese-iron-based sodium-containing oxide, the general chemical formula of which is Na. q Ni x Mn y Fe z M pO2, wherein 0 < q ≤ 1, 0 < x, 0 < y, 0 < z, 0 ≤ p, x + y + z ≥ 0.81, x + y + z + p ≤ 1, and M includes one or more of V, Cr, Zn, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, and Ir, and the total mass percentage of Ni, Mn, and Fe is 40% to 50%.

[0100] By employing a positive electrode active material with this structural characteristic in the positive electrode sheet, the rebound rate of the positive electrode sheet under full charge can be reduced compared to the rebound rate before full charge. This results in the full charge group margin of the battery cell 30 being lower than the maximum group margin before full charge, which is beneficial for improving the energy density of the battery cell 30 and reducing the expansion force of the battery cell 30 under high group margin. This phenomenon is speculated to occur because during the phase reconstruction process of the positive electrode active material, as cycling progresses, the crystal structure of the reconstructed phase in the mixed phase, after being extracted to the maximum interlayer spacing, is not easily reversed back to the initial phase. Therefore, the gradual increase in the proportion of the reconstructed phase leads to an increase in expansion force. Furthermore, as the operating voltage continues to increase, some phases collapse, leading to expansion and contraction.

[0101] The lower limit of the operating voltage of the battery cell 30 is 1.5V to 2.0V, and the upper limit of the operating voltage of the battery cell 30 is 3.7V to 4.2V. The ratio of the maximum thickness of the electrode assembly 32 in the fully charged state of the battery cell 30 to the thickness of the first wall 311 is 16 to 165.

[0102] "Usage voltage lower limit" refers to the lower voltage limit of battery cell 30 during discharge. For example, battery cell 30 stops discharging when it reaches the usage voltage lower limit after being fully charged. For example, the usage voltage lower limit of battery cell 30 can be any one of 1.5V, 1.55V, 1.6V, 1.65V, 1.7V, 1.75V, 1.8V, 1.85V, 1.9V, 1.95V, 2.0V, or a range between any two of these values.

[0103] "Usage voltage limit" refers to the upper limit of the power supply when the battery cell 30 is charging. For example, the battery cell 30 is charged from 0% state of charge to the usage voltage limit and then charging stops. For example, the usage voltage limit of the battery cell 30 can be any one of 3.7V, 3.75V, 3.8V, 3.85V, 3.9V, 3.95V, 4.0V, 4.05V, 4.1V, 4.15V, 4.2V, or a range between any two of these values.

[0104] The housing 31 has a receiving cavity in which the electrode assembly 32 is assembled.

[0105] The first wall 311 is a wall portion constituting the outer shell 31. There are two first walls 311, which are arranged opposite to each other in the thickness direction of the electrode assembly 32, and the electrode assembly 32 is disposed between the two first walls 311.

[0106] In some embodiments, the housing 31 includes a housing 312 and an end cap 313. The housing 312 has an opening, and the end cap 313 closes the opening to form a receiving cavity. The housing 312 includes two first walls 311 disposed opposite each other along a first direction X, and two second walls 314 disposed opposite each other along the length direction Y of the battery cell. Each first wall 311 connects to the two second walls 314. The housing 312 also includes a third wall 315, around which the two first walls 311 and the two second walls 314 surround. The third wall 315 and the end cap 313 are disposed opposite each other in the height direction of the battery cell (as shown in the Z direction of FIG3). The first direction X may be parallel to the width direction of the battery cell, the thickness direction of the first wall 311 is parallel to the first direction X, and the first direction X, the length direction Y of the battery cell, and the height direction of the battery cell are perpendicular to each other.

[0107] The battery cell 30 also includes an electrode terminal 33, which is disposed on the end cover 313. The electrode terminal 33 is electrically connected to the tab of the electrode assembly 32 through an adapter 34.

[0108] The electrode assembly 32 has a flat structure. The thickness direction of the electrode assembly 32 is parallel to the thickness direction of the first wall. The first wall 311 can be set to correspond to the large surface of the electrode assembly 32. The first wall 311 can be the large surface of the outer shell 31.

[0109] When the electrode assembly 32 has a stacked structure, the thickness direction of the electrode assembly 32 refers to the direction of the electrode stacking. When the electrode assembly 32 has a wound structure, the electrode assembly 32 is flat and includes a flat region and a bent region. The thickness direction of the electrode assembly 32 is the stacking direction of the electrode in the flat region, and the thickness direction of the electrode assembly 32 is perpendicular to the winding axis direction of the electrode assembly 32.

[0110] The thickness of electrode assembly 32 refers to its dimension in the first direction X. Referring to Figure 4, dimension W1 represents the thickness of electrode assembly 32, and dimension W2 represents the thickness of the first wall 311. For a single battery cell 30, the thickness of the first wall 311 is constant and remains unchanged with voltage changes. However, the thickness of electrode assembly 32 changes with voltage changes.

[0111] When multiple electrode assemblies 32 are disposed inside the housing 31, the maximum thickness of the electrode assembly 32 in the fully charged state of the battery cell 30 refers to the maximum dimension of the multiple electrode assemblies 32 as a whole in the first direction X.

[0112] In some embodiments, the method for measuring the maximum thickness of the electrode assembly 32 is as follows: at 25°C, the battery cell 30 is scanned along the height direction of the battery cell using a nanoVoxel-5000 CT system to obtain a tomographic image of the electrode assembly 32, and the maximum size of the tomographic image in the first direction X is measured.

[0113] One method for measuring the thickness of the first wall 311 is to disassemble the battery cell 30 and measure the thickness of the first wall 311 with a micrometer.

[0114] Another method for measuring the thickness of the first wall 311 is as follows: at 25°C, use a nanoVoxel-5000 CT system to scan the battery cell 30 along the height direction of the battery cell to obtain a cross-section (tomographic image) of the outer casing 31. On the obtained cross-section, measure the dimension of the first wall 311 in the first direction X.

[0115] For example, the ratio of the maximum thickness of the electrode assembly 32 in the fully charged state of the battery cell 30 to the thickness of the first wall 311 can be any one of the following values ​​or a range between any two values: 16, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, and 165.

[0116] According to the battery cell 30 of this application embodiment, the cell characteristics of the positive electrode active material can make the rebound rate of the positive electrode sheet under full charge less than the rebound rate before full charge. When the lower limit of the operating voltage of the battery cell 30 is 1.5V to 2.0V and the upper limit of the operating voltage of the battery cell 30 is 3.7V to 4.2V, the expansion force of the battery cell 30 shows a trend of first increasing and then decreasing when charging within this range. During a single charge, the expansion force of the battery cell 30 shows a trend of first increasing and then decreasing. The ratio of the maximum thickness of the electrode assembly 32 in the fully charged state of the battery cell 30 to the thickness of the first wall 311 satisfies the above relationship. Under the premise of safety, the first wall 311 can be designed to be thinner to improve the energy density of the battery cell 30; or, the thickness of the electrode assembly 32 can be designed to be thicker, so that as much electrode active material as possible can be placed in the outer shell 31 of the battery cell 30 under the premise of safety, thereby improving the energy density of the battery cell 30.

[0117] In some embodiments, the ratio of the maximum thickness of the electrode assembly 32 in the fully charged state of the battery cell 30 to the thickness of the first wall 311 is 55 to 75.

[0118] Compared to configuring the ratio of the maximum thickness of the aforementioned electrode assembly 32 to the thickness of the first wall 311 to be 16 to 165, when the ratio of the thickness of the electrode assembly 32 to the thickness of the first wall 311 in the fully charged state of the battery cell 30 is 55 to 75, the energy density of the battery cell 30 can be further improved while ensuring that the expansion force increases very little.

[0119] In some embodiments, the thickness of the electrode assembly 32 in the fully charged state of the battery cell 30 is 20 mm to 80 mm.

[0120] Optionally, the thickness of the electrode assembly 32 in the fully charged state of the battery cell 30 is 20mm to 65mm.

[0121] For example, the thickness of the electrode assembly 32 in the fully charged state of the battery cell 30 can be any one of 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm or any range between two of these values.

[0122] The thickness of the electrode assembly 32 in the fully charged state of the battery cell 30 meets the above range, the expansion rate of the electrode assembly 32 is small, and the expansion force of the battery cell 30 is small.

[0123] In this application, the battery cell 30 can be a pouch battery cell or a square hard-shell battery cell. The first wall 311 can be the large surface of the outer casing of the battery cell 30, and the first wall 311 can be the wall with the largest outer surface area among all the walls of the outer casing 31.

[0124] In some embodiments, the outer shell 31 is a steel shell with a Young's modulus of 180 to 190 GPa and a thickness of 0.3 mm to 0.9 mm for the first wall 311.

[0125] For example, the Young's modulus of the outer shell 31 can be any one of 180 GPa, 181 GPa, 182 GPa, 183 GPa, 184 GPa, 185 GPa, 186 GPa, 187 GPa, 188 GPa, 189 GPa, or 190 GPa, or a range between any two of these values.

[0126] The thickness of the first wall 311 can be any one of the following values, or a range between any two values: 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.75mm, 0.8mm, 0.85mm, and 0.9mm.

[0127] Optionally, the thickness of the first wall 311 is 0.4 mm to 0.9 mm.

[0128] In the above scheme, since the expansion force of the battery cell 30 when fully charged is less than the maximum expansion force before full charge, and the expansion growth is very small or even shows a contraction trend in the later stage of cycle, a low Young's modulus steel shell can be selected when designing the cell, resulting in lower material costs. The thickness of the first wall 311 meets the above range. With the first wall 311 having high resistance to deformation, the thickness of the electrode assembly 32 can be thicker and / or the thickness of the first wall 311 can be thinner, thereby resulting in a higher energy density of the battery cell 30.

[0129] In some embodiments, the outer shell 31 is an aluminum shell with a Young's modulus of 65 GPa to 70 GPa and a thickness of 0.4 mm to 1.2 mm for the first wall 311.

[0130] For example, the Young's modulus of the outer shell 31 can be any one of 65 GPa, 66 GPa, 67 GPa, 68 GPa, 69 GPa, 70 GPa, or a range between any two of these values.

[0131] The thickness of the first wall 311 can be any one of the following values, or a range between any two values: 0.3mm, 0.35mm, 0.4mm, 0.45mm, 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, 0.75mm, 0.8mm, 0.85mm, 0.9mm, 0.95mm, 1mm, 1.05mm, 1.1mm, 1.15mm, and 1.2mm.

[0132] Optionally, the thickness of the first wall 311 can be 0.4mm to 0.9mm.

[0133] In the above scheme, since the expansion force of the battery cell 30 when fully charged is less than the maximum expansion force before full charge, the Young's modulus of the aluminum shell can be smaller, the material cost is lower, the thickness of the first wall 311 meets the above range, the first wall 311 has a high resistance to deformation, while the thickness of the electrode assembly 32 can be thicker and / or the thickness of the first wall 311 can be thinner, thereby the energy density of the battery cell 30 is higher.

[0134] In some embodiments, the outer shell 31 is an aluminum-plastic film, the Young's modulus of the outer shell 31 is 70 GPa to 80 GPa, and the thickness of the first wall 311 can be 100 μm to 300 μm.

[0135] For example, the Young's modulus of the outer shell 31 can be any one of 70 GPa, 71 GPa, 72 GPa, 73 GPa, 74 GPa, 75 GPa, 76 GPa, 77 GPa, 78 GPa, 79 GPa, 80 GPa or a range between any two of these values.

[0136] For example, the thickness of the first wall 311 can be any one of the following values, or a range between any two values: 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm, 210μm, 220μm, 230μm, 240μm, 250μm, 260μm, 270μm, 280μm, 290μm, and 300μm.

[0137] Optionally, the thickness of the first wall 311 can be 120μm to 200μm.

[0138] In the above scheme, since the expansion force of the battery cell 30 when fully charged is less than the maximum expansion force before full charge, the Young's modulus of the aluminum-plastic film can be smaller, and the material cost is lower; the thickness of the first wall 311 meets the above range, and when the first wall 311 has a high resistance to deformation, the thickness of the electrode assembly 32 can be thicker and / or the thickness of the first wall 311 can be thinner, and the energy density of the battery cell 30 is higher.

[0139] In some embodiments, the outer casing 31 is an aluminum casing, and the electrode assembly 32 includes a negative electrode sheet, a negative electrode current collector, and a negative electrode tab 321. The battery cell 30 also includes a negative electrode lead 35, which is disposed on the outer casing 31 and serves to electrically connect the negative electrode tab 321 to a conductor outside the battery cell 30. The negative electrode lead 35 is composed of aluminum, with the mass percentage of aluminum exceeding the mass percentage of the other elements.

[0140] The negative electrode lead-out portion 35 can be referred to as the negative electrode terminal, and the negative electrode lead-out portion 35 can be provided on the end cover 313. The negative electrode lead-out portion 35 is internally electrically connected to the negative electrode tab 321, and externally electrically connected to the conductor (such as a busbar, a switch, etc.) outside the battery cell 30.

[0141] In some embodiments, the negative electrode lead-out portion 35 can be an integral structure, with a portion of the negative electrode lead-out portion 35 located on the side of the end cover 313 facing away from the inside of the battery cell 30, and a portion of the negative electrode lead-out portion 35 located on the side of the end cover 313 facing the inside of the battery cell 30.

[0142] In some embodiments, the negative electrode lead-out portion 35 can be a split structure, and the negative electrode lead-out portion 35 includes a negative electrode external connection portion and a negative electrode internal connection portion. The negative electrode external connection portion is used to electrically connect with a conductor outside the battery cell 30, and the negative electrode internal connection portion is electrically connected with the negative electrode tab 321.

[0143] In the above scheme, the outer casing 31 is made of aluminum, and the negative electrode lead 35 is made of aluminum. Aluminum has a lower material cost and is lighter in weight. When the battery cell 30 is a sodium-ion battery system, sodium and aluminum do not undergo an alloying reaction at low potentials. Using aluminum as the material for the negative electrode lead 35, compared to copper and copper-aluminum composite materials, can reduce the material cost of the battery cell 30 and lighten its weight.

[0144] In some embodiments, during a single charge, the rebound rate of the positive electrode sheet contained in the electrode assembly 32 exhibits a trend of first increasing and then decreasing. The rebound rate of the positive electrode sheet refers to the percentage increase in the thickness of the positive electrode sheet, i.e., the rebound rate of the positive electrode sheet = (positive electrode sheet thickness after charging - initial positive electrode sheet thickness) / initial positive electrode sheet thickness * 100%. The thickness of the positive electrode sheet can be measured using a micrometer.

[0145] The expansion of the battery cell 30 mainly originates from the thickness expansion of the electrode sheet. During a single charge, the rebound rate of the positive electrode sheet shows a trend of first increasing and then decreasing. That is, as the state of charge of the battery cell 30 increases from 0% to 100%, the rebound rate of the positive electrode sheet first increases and then decreases, and the corresponding expansion force also first increases and then decreases. Therefore, the increase rate of expansion force of the battery cell 30 after full charge is relatively small compared to the expansion force before charging.

[0146] In some embodiments, when the state of charge of the battery cell 30 is 45% to 65%, the rebound rate of the positive electrode is 5% to 8%, optionally 5% to 6%; for example, it can be any one of 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8% or a range between any two of these values.

[0147] When the state of charge of the battery cell 30 is greater than 65%, the rebound rate of the positive electrode is less than or equal to 5%.

[0148] When the state of charge (SOC) is between 45% and 65%, the positive electrode exhibits a high rebound rate. However, as the SOC increases, the rebound rate decreases. This is beneficial because it reduces the full-charge group margin of the battery cell 30 to the maximum group margin before full charge, thereby increasing the energy density of the battery cell 30 and reducing the expansion force of the battery cell 30 under high group margin conditions. Group margin refers to the ratio of the actual size of the electrode assembly 32 to the size of the cavity in the housing 312. For example, taking the group margin in the width direction as an example, the group margin in the width direction refers to the ratio between the maximum thickness of the electrode assembly 32 and the size of the cavity in the housing 312 in the width direction (first direction X) of the battery cell. The size of the cavity in the width direction of the housing 312 is a constant value, which is the size of the cavity in the width direction of the housing 312 when the electrode assembly 32 is inserted into the housing. For example, the size of the inner surface of the second wall 314 in the width direction of the battery cell is the size of the cavity in the width direction of the housing 312.

[0149] In some embodiments, when the state of charge of the battery cell 30 is 80% to 95%, the rebound rate of the positive electrode is 2% to 4.5%, optionally 2% to 3%; for example, it can be any one of 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or a range between any two of these values.

[0150] When the state of charge of the battery cell 30 is 95% to 100%, the rebound rate of the positive electrode is 0% to 1.9%, optionally 0% to 1.5%, for example, it can be any one of 0%, 0.5%, 1%, 1.5%, 1.9%, or a range between any two of the above values.

[0151] When the charge is close to full charge, as the state of charge increases, the rebound rate of the positive electrode gradually decreases. This allows the full charge margin of the battery cell 30 to be less than the maximum margin before full charge, which is beneficial to improving the energy density of the battery cell 30 and reducing the expansion force of the battery cell 30 under high margin.

[0152] The state of charge (SOC) of the battery cell 30 can be directly obtained by relevant analytical instruments, such as an in-situ expansion analyzer or an electrochemical workstation, or by referring to GB / T 31486-2015. For example, the SOC testing method is as follows: First, estimate the total discharge capacity A of the battery according to the lithium battery rated capacity test standard in GB / T 31486-2015; then, after charging the battery to SOC B, discharge it to 0% SOC to release capacity b (charge and discharge conditions refer to GB / T 31486-2015); calculate the battery SOC B = b / A * 100%.

[0153] In some embodiments, the positive electrode active material includes nickel-manganese-iron-based sodium oxide.

[0154] The general chemical formula for nickel-manganese-iron-based sodium-containing oxides is Na. q Ni x Mn y Fe z M p O2, where 0 < q ≤ 1, 0 < x, 0 < y, 0 < z, 0 ≤ p, x + y + z ≥ 0.81, x + y + z + p ≤ 1, and M includes one or more of V, Cr, Zn, Al, Sc, Sn, Sb, Zr, Nb, Ti, Mg, Cu, Ru, and Ir.

[0155] Layered oxide Na q Ni x Mn y Fe z M p The c-axis unit cell length of O2 initially increases and then decreases with increasing sodium removal. Using Na... q Ni x Mn y Fe z M p O2 serves as the positive electrode active material; during charging, Na... q Ni x Mn y Fe z M p O2 undergoes a sodium removal reaction, and as the charging voltage gradually increases, or as the state of charge of the battery cell 30 gradually increases, Na... q Ni x Mn y Fe z M p The amount of sodium removed from O2 also increases, then Na q Ni x Mn y Fe z M p The c-axis unit cell length of O2 first increases and then decreases, as shown in Figures 5 and 6. In Figure 5, the vertical axis represents the c-axis unit cell length, which increases from smallest to largest according to the direction of the arrows. Figure 5 shows the increase in sodium removal amount, i.e., Na... q Ni x Mn y Fe z M p As the Na content of O2 decreases, its c-axis cell length first increases and then decreases. Figure 6 shows the Na content (referring to the subscript q of Na) of 0.89. q Ni x Mn y Fe z M pThe change in cell structure during the process of removing sodium from O2 (Na0.89) to a Na content of 0.11 (Na0.11). This cell structure characteristic leads to the change in Na... q Ni x Mn y Fe z M p During the charging process, O2 exhibits a macroscopic phenomenon of first expanding and then contracting, which in turn causes the rebound rate of the positive electrode to also exhibit the characteristic of first expanding and then contracting. Consequently, the full charge margin of the battery cell 30 is less than the maximum margin before full charge, which is beneficial to improving the energy density of the battery cell 30 and reducing the expansion force of the battery cell 30 under high margin.

[0156] In some embodiments, the total mass percentage of Ni, Mn, and Fe in the nickel-manganese-iron-based sodium-containing oxide is 40%–50%, optionally 42%–46%, for example, it can be any one or a range between any two of 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, and 50%. At this ratio, Na… q Ni x Mn y Fe z M p The c-axis cell length of O2 shows a trend of first increasing and then decreasing with the increase of sodium removal.

[0157] In some embodiments, the general chemical formula of the nickel-manganese-iron-based sodium-containing oxide satisfies 0.1 ≤ q ≤ 1, optionally 0.2 ≤ q ≤ 0.9, and even more optionally 0.4 ≤ q ≤ 0.6. For example, q can be, but is not limited to, any one of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1, or a range between any two of these values. q can reflect the Na content in the positive electrode active material. With a suitable Na content, the positive electrode active material can provide active Na during the charging and discharging process of the battery cell. + This promotes the electrochemical reaction of the battery cell 30, which is beneficial to improving the energy density of the battery cell 30.

[0158] In some embodiments, the general chemical formula of the nickel-manganese-iron-based sodium oxide satisfies 0.1≤x≤0.5, and optionally, 0.2≤x≤0.4. For example, x can be any one of 0.1, 0.2, 0.3, 0.4, 0.5 or a range between any two of the point values.

[0159] In some embodiments, the general chemical formula of the nickel-manganese-iron-based sodium oxide satisfies 0.1≤y≤0.5, and optionally, 0.2≤y≤0.4. For example, y can be any one of 0.1, 0.2, 0.3, 0.4, 0.5 or a range between any two of the point values.

[0160] In some embodiments, the general chemical formula of the nickel-manganese-iron-based sodium oxide satisfies 0.1≤z≤0.5, for example, z can be any one of 0.1, 0.2, 0.3, 0.4, 0.5 or a range between any two of these values.

[0161] In some embodiments, the general chemical formula of the nickel-manganese-iron-based sodium oxide satisfies 0.2≤z≤0.3.

[0162] The molar proportion of Fe in the entire cathode material is 0.2-0.3%. Excessive Fe doping can lead to the migration of the transition metal layer, causing irreversible changes in the crystal structure and deteriorating the lifespan of the battery cell. Insufficient Fe can prevent the material from effectively suppressing phase transitions, resulting in a decrease in the power performance of the battery cell.

[0163] In some embodiments, the general chemical formula of the nickel-manganese-iron-based sodium oxide satisfies 0.8≤x+y+z≤1, and optionally, 0.9≤x+y+z≤1. For example, x+y+z can be any one of 0.8, 0.85, 0.9, 0.95, 1, or a range between any two of the point values.

[0164] In some embodiments, the general chemical formula of the nickel-manganese-iron-based sodium oxide satisfies 0 ≤ p ≤ 0.2, and optionally, 0 ≤ p ≤ 0.1. For example, p can be any one of 0, 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, 0.15, 0.2 or a range between any two of these values.

[0165] In some embodiments, when the state of charge of the battery cell 30 is 0%, Na q Ni x Mn y Fe z M p The c-axis unit cell length of O2 is c1. For example, it could be The range between any one or both of the point values ​​in the range;

[0166] When the state of charge of cell 30 is 50%–60%, Na q Ni x Mn y Fe z M p The c-axis unit cell length of O2 is c2. For example, it could be The range between any one or both of the point values ​​in the range;

[0167] When the state of charge of cell 30 is 95%–100%, Na q Ni x Mn y Fe z M p The c-axis unit cell length of O2 is c3. For example, it could be The range between any one or both of the point values ​​in the range; and c1 < c2, c3 < c2.

[0168] The cell length can be determined by measuring the interplanar spacing of the material using X-ray diffraction combined with Bragg's equation, and then calculated using the formula relating interplanar spacing to cell length. As the state of charge increases, Na... q Ni x Mn y Fe z M p The c-axis cell length of O2 first increases and then decreases, which is beneficial to control the full charge group margin of the battery cell 30 to be less than the maximum group margin before full charge, which is beneficial to improve the energy density of the battery cell 30 and reduce the expansion force of the battery cell 30 under high group margin.

[0169] In some embodiments, the electrode assembly 32 includes a negative electrode sheet containing a negative electrode active material. The porosity of the negative electrode active material is 40% to 70%, optionally 45% to 55%, for example, it can be any one of 40%, 42%, 45%, 46%, 48%, 50%, 52%, 54%, 55%, 56%, 58%, 60%, 62%, 64%, 65%, 66%, 68%, 70%, or a range between any two values. The porosity of the negative electrode active material can be obtained by gas adsorption. The abundant pores of the negative electrode active material facilitate the full wetting of it by the electrolyte, thereby enabling the active ions in the battery cell 30 to be effectively transported between the positive and negative electrode sheets through the electrolyte, improving ion transport efficiency and enhancing the electrochemical performance of the battery cell 30. Meanwhile, the presence of more pores can also buffer the volume expansion of the negative electrode sheet when active ions are embedded in the negative electrode active material and volume expansion occurs.

[0170] In some embodiments, the average pore size of the negative electrode active material is 1 nm to 30 nm, optionally 1 nm to 10 nm, for example, it can be any one or a range between any two of the following values: 1 nm, 2 nm, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, 22 nm, 24 nm, 26 nm, 28 nm, and 30 nm. The average pore size of the negative electrode active material can be obtained by gas adsorption. Nanopores facilitate the entry of electrolyte into the interior of the negative electrode active material through capillary forces, thereby improving the electrolyte wetting performance of the negative electrode sheet.

[0171] In some embodiments, the negative electrode active material includes hard carbon. Hard carbon has low expansion force, and using it as a negative electrode active material helps to reduce the expansion force of the negative electrode during charging and discharging, thereby reducing the expansion force of the battery cell 30.

[0172] For more detailed technical features of each group of components in the battery cell 30, please refer to the following:

[0173] 1. Electrode assembly

[0174] Electrode assembly is an important component of a battery cell, and it typically includes a positive electrode, a negative electrode, and a separator. When the secondary battery is a solid-state battery, the electrode assembly may include a positive electrode, a solid electrolyte, and a negative electrode.

[0175] [Positive electrode plate]

[0176] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0177] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0178] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0179] In some embodiments, the battery cell is a sodium-ion battery, and the positive electrode active material can be a positive electrode active material known in the art for use in sodium-ion batteries. As an example, the positive electrode active material may include sodium transition metal oxides, polyanionic compounds, Prussian blue compounds, etc., and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries can also be used. For example, as an optional technical solution in this application, the transition metal in the sodium transition metal oxide can be at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The sodium transition metal oxide is, for example, Na. x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, 0 <x≤1。

[0180] As an optional technical approach in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents (YO4). n- The valence state. Polyanionic compounds can also have sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl, and Br. Polyanionic compounds can also have sodium ions, tetrahedral (YO4) valence states. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be at least one of P, S, and Si, and n represents (YO4). n- Valence state: Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; the halogen can be at least one of F, Cl, and Br. Examples of polyanionic compounds include NaFePO4, Na3V2(PO4)3, NaM'PO4F (M' is one or more of V, Fe, Mn, and Ni), and Na3(VO4)2(PO4)3. y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0181] As an optional technical solution of the present application, the polyanionic compound may be Na x-a A a V y-b M b (PO4) 2-2c (DO4) 2c F z-d Q d , where the A element represents an alkali metal element that dopes and replaces the Na element, the M element represents a metal element that replaces the V element, the D element represents a doping element that replaces the P element, and the Q element represents a doping element that replaces the F element. The D element includes at least one of Si and S; the Q element includes at least one of Cl and O; 3.5 ≤ x ≤ 4.5, 0 ≤ a ≤ 0.15x, 0.8 ≤ y ≤ 1.1, 0 ≤ b ≤ 0.3y, 0 ≤ c ≤ 0.15, 0.8 ≤ z ≤ 1.1, 0 ≤ d ≤ 0.2z. Optionally, the A element includes at least one of K and Li; the M element includes at least one of Fe, Cr, Al, Sc, Ga, In, Ti, Zr, Mn, Zn, Ni, Cu, and Co.

[0182] As an optional technical solution of the present application, the polyanionic compound may be Na x R y (PO4)2P2O7, where x = 3.5 - 4.5, y = 2.75 - 3.25, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W, and Pb.

[0183] As an optional technical solution of the present application, the polyanionic compound may be Na 4+x R 3-y P 4-m O 15 / C; where 0 < x < 0.5, 0 < y ≤ 0.5, 0 < m ≤ 0.2, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Cr, Nb, Mo, In, Ga, Sn, Hf, Ta, W, and Pb.

[0184] The Prussian blue compounds may be a class of compounds having sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue compounds are, for example, Na a Me b Me’ c(CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0 <a≤2,0<b<1,0<c<1。

[0185] In some embodiments, the positive electrode active material includes at least one of sodium-containing layered oxides, polyanionic sodium compounds, and Prussian blue sodium compounds.

[0186] In some embodiments, the sodium-containing layered oxide is an iron-manganese layered oxide, specifically including at least one of nickel-iron-manganese layered oxide and copper-iron-manganese layered oxide.

[0187] During the charging and discharging process, active ions (Na+) are intercalated and deintercalated, resulting in a different molar content of Na at different discharge states. In the examples of positive electrode active materials in this application, the molar content of Na refers to the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar content of Na changes after charge-discharge cycles.

[0188] In the examples of positive electrode active materials in this application, the molar content of oxygen is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of oxygen will fluctuate.

[0189] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0190] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0191] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0192] [Negative electrode plate]

[0193] The negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector.

[0194] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0195] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil or copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0196] In some embodiments, the negative electrode film layer includes a negative electrode active material. The negative electrode active material may be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0197] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0198] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0199] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0200] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0201] In other embodiments, the current collector of the negative electrode sheet typically includes a current collector body and a base coating. The base coating can be disposed on at least one side of the current collector body. The base coating basically does not contain negative electrode active material, and may include a small amount of carbon material. However, the carbon material forms a thin coating and cannot function as a negative electrode active material. In this embodiment, the negative electrode sheet can be an electrode sheet without a negative electrode active material layer. For a negative electrode sheet without a negative electrode active material layer, when the current collector of the negative electrode sheet does not contain a base coating, the film layer can be disposed on the surface of at least one side of the current collector; when the current collector of the negative electrode sheet includes a base coating, the film layer can be disposed on the surface of the base coating away from the current collector.

[0202] In some embodiments, the film layer may further include a binder for fixing the additive to the negative electrode sheet. The type of binder is not particularly limited, and those skilled in the art can choose flexibly according to actual needs.

[0203] [Electrolytes]

[0204] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0205] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0206] In some embodiments, the battery cell is a sodium-ion battery, and the electrolyte salt may be selected from at least one of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium hexafluoroarsenate, sodium difluorosulfonamide, sodium ditrifluoromethanesulfonamide, sodium trifluoromethanesulfonate, sodium difluorophosphate, sodium difluorooxalate borate, sodium dioxalate borate, sodium difluorodioxalate phosphate, and sodium tetrafluorooxalate phosphate.

[0207] In some embodiments, the battery cell is a lithium-ion battery, and the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0208] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0209] In some embodiments, the solvent of the electrolyte in the sodium-ion battery includes carbonates, which include at least one of ethylene carbonate, propylene carbonate, or fluoroethylene carbonate.

[0210] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0211] [Isolation membrane]

[0212] In some embodiments, the battery cell also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0213] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0214] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0215] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0216] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0217] A second aspect of this application provides a battery 100, including the aforementioned battery cell 30.

[0218] Referring to Figure 7, the battery 100 includes a plurality of battery cells 30, which are arranged along the first direction X to form a battery cell group 11. The battery 100 also includes two end plates 40, which are respectively disposed on both sides of the battery cell group 11 in the first direction X, so as to clamp and fix the battery cell group 11.

[0219] The first direction X can be parallel to the length direction of battery 100.

[0220] The end plate 40 is a component disposed at the end of the battery cell pack 11, and the end plate 40 can protect the battery cell pack 11 in the first direction X.

[0221] The two end plates 40 clamp and fix the battery cell group 11, which can limit the expansion and deformation of the battery cell group 11 in the first direction X.

[0222] According to the embodiment of this application, the battery 100 has two end plates 40 respectively disposed on both sides of the battery cell assembly 11 in the first direction X, so as to clamp and fix the battery cell assembly 11, and at the same time, to protect the battery cell assembly 11 in the first direction X, reducing the risk of damage to the battery cell assembly 11.

[0223] In some embodiments, the end plate 40 is made of aluminum alloy and has a Young's modulus of 60 GPa to 70 GPa.

[0224] For example, the Young's modulus of end plate 40 can be any one of 60 GPa, 61 GPa, 62 GPa, 63 GPa, 64 GPa, 65 GPa, 66 GPa, 67 GPa, 68 GPa, 69 GPa, 70 GPa or a range between any two of these values.

[0225] The end plate 40 is made of aluminum alloy, which is lightweight and has high strength.

[0226] In some embodiments, the thickness direction of the end plate 40 is parallel to the first direction X, and the thickness of the end plate 40 is 20mm to 35mm.

[0227] For example, the thickness of the end plate 40 can be any one of 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm, 31mm, 32mm, 33mm, 34mm, or 35mm, or a range between any two of these values.

[0228] The thickness direction of the end plate 40 is parallel to the first direction X. The end plate 40 occupies a small assembly space, and the battery 100 can have a high energy density.

[0229] The thickness of the end plate 40 satisfies the above relationship. On the one hand, it can constrain the expansion and deformation of the battery cell 30; on the other hand, it occupies less assembly space, and the battery 100 can have a higher energy density.

[0230] In some embodiments, the battery 100 further includes a busbar 60, through which two adjacent battery cells 30 are connected. The busbar 60 is a flat plate.

[0231] The merging member 60 includes a first surface and a second surface disposed opposite to each other along the thickness direction of the merging member 60, and the first surface and the second surface are two planes that are parallel to each other.

[0232] Optionally, the thickness direction of the busbar 60 is perpendicular to the first direction X.

[0233] The aforementioned battery cell 30 has low expansion force, and the structure of the busbar 60 can be relatively simple, without the need for additional buffer structure.

[0234] The busbar component 60 is a flat plate, which has a simple structure and is easy to process and manufacture.

[0235] Please refer to Figures 2 and 7, and further refer to Figure 8. In some embodiments, the battery 100 also includes a housing 20, and the battery cell group 11 is disposed inside the housing 20 and bonded to the bottom wall 23 of the housing 20.

[0236] The battery cell assembly 11 is bonded to the bottom wall 23 of the housing 20 to facilitate the positioning of the battery cell assembly 11 and thereby restrict the positional movement of the battery cell assembly 11 relative to the housing 20.

[0237] In some embodiments, the battery 100 further includes a restraint member 50, which is sleeved on the two end plates 40 and the battery cell assembly 11 to fix the two end plates 40 to the battery cell assembly 11.

[0238] The restraint member 50 is ring-shaped, and the two end plates 40 and the battery cell group 11 are together fitted by the restraint member 50, thereby restraining and fixing the two end plates 40 and the battery cell group 11.

[0239] The restraint 50 is designed to secure the battery cell assembly 11.

[0240] Referring to Figure 7, in some embodiments, the restraint member 50 includes a first restraint member 51, which is a steel strap or a plastic strap.

[0241] The first restraint member 51 is fitted onto the two end plates 40 and the battery cell assembly 11. When the first restraint member 51 is a steel strip, the steel strip has high strength and provides good restraint for the battery cell assembly 11. When the first restraint member 51 is a plastic strip, the production cost is low while meeting the restraint strength requirements.

[0242] In some embodiments, the restraint member 50 includes a first restraint member 51, and there are two first restraint members 51. The two first restraint members 51 are spaced apart along a second direction Z, which is parallel to the thickness direction of the bottom wall 23. The first restraint member 51 is a plastic strip.

[0243] The second direction Z can be parallel to the height direction of the battery cell.

[0244] The number of first restraint components 51 is two. The first restraint component 51 is a plastic strip, which has low production cost while meeting the restraint strength requirements.

[0245] Referring to Figure 8, in some embodiments, the restraint member 50 includes a first restraint member 51 and a second restraint member 52. The first restraint member 51 and the second restraint member 52 are spaced apart in a second direction Z, which is parallel to the thickness direction of the bottom wall 23. The first restraint member 51 is farther away from the bottom wall 23 relative to the second restraint member 52, and the strength of the first restraint member 51 is greater than the strength of the second restraint member 52.

[0246] When the first restraint member 51 and the second restraint member 52 are spaced apart in the second direction Z, since the battery cell assembly 11 is bonded to the bottom wall 23 of the housing 20, the strength of the second restraint member 52 can be less than that of the first restraint member 51. The second restraint member 52 and the first restraint member 51 can be made of different materials, thereby reducing production costs.

[0247] In some embodiments, the first restraint member 51 is a steel strap and the second restraint member 52 is a plastic strap.

[0248] The first restraint component 51 is a steel strip, which has good strength and provides good constraint on the battery cell pack 11. Under the premise of meeting the restraint requirements, the second restraint component 52 is a plastic strip, which can reduce costs.

[0249] In some embodiments, when there are multiple restraint members 50 and the multiple restraint members 50 are spaced apart in the second direction Z, the strength of the restraint member 50 near the bottom wall 23 may be less than the strength of the other restraint members 50.

[0250] This application embodiment also provides an electrical device, which includes the above-mentioned battery cell 30 or the above-mentioned battery 100.

[0251] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0252] Example 1

[0253] This embodiment provides a sodium secondary battery cell, which includes a positive electrode, a negative electrode, a separator, and an electrolyte. The active material in the positive electrode is Na, with a molar mass ratio of Ni, Fe, and Mn of 45.5%. 0.96 Ni 0.22 Mn 0.33 Fe 0.33 Zn 0.08 O2, the active material of the negative electrode is hard carbon with a porosity of 50.6% and an average pore size of 40nm.

[0254] This sodium-based secondary battery cell can be prepared using the following method:

[0255] (1) Positive electrode plate

[0256] positive electrode activity 材 Material (Na 0.96 Ni 0.22 Mn 0.33 Fe 0.33 Zn 0.08 O2), conductive agent (conductive carbon black) ) The binder (polyvinylidene fluoride, PVDF) was thoroughly mixed in a solvent (N-methylpyrrolidone, NMP) to obtain the positive electrode slurry. The mass ratio of the positive electrode active material, solvent, conductive agent, and binder was 95:35:3:2. The positive electrode slurry was coated onto both surfaces of a current collector (aluminum foil), with a single-sided area of ​​1540.25 mm². 2 The single-sided loading of the positive electrode active material on the current collector was 300 mg. After drying and cold pressing, a compacted density of 3.1 g / cm³ was obtained. 3 The positive electrode sheet.

[0257] (2) Negative electrode plate

[0258] The negative electrode active material (hard carbon), conductive agent (conductive carbon black), and binder (carboxymethyl cellulose, CMC) were thoroughly mixed in deionized water to obtain a negative electrode slurry. The mass ratio of the negative electrode active material, deionized water, conductive agent, and binder was 95:50:2:3. The negative electrode slurry was then coated onto a current collector (copper foil), with a single-sided area of ​​1540.25 mm². 2 The material was dried and cold-pressed to obtain a compacted density of 0.95 g / cm³. 3 The negative electrode sheet.

[0259] (3) Electrolyte

[0260] A 1 mol / L NaPF6 solution was used as the electrolyte, which was a mixed solvent of ethylene carbonate EC: propylene carbonate PC: fluoroethylene carbonate FEC = 47.5: 47.5: 5 (volume ratio).

[0261] (4) Separating membrane

[0262] Polyethylene film is used as the separation membrane.

[0263] (5) Sodium secondary battery cell

[0264] The positive electrode sheet, polyethylene film, and negative electrode sheet are stacked in sequence and wound to form a square electrode assembly (bare cell). The electrode assembly is then pressed into a flat shape. The bare cell is placed into a square aluminum shell, electrolyte is added, and the shell is sealed to produce a square-shell sodium secondary battery cell. It is then formed and left to stand.

[0265] To ensure that the bare cell has sufficient expansion space in the square aluminum casing, the initial value of the width direction group margin of the sodium secondary battery cell is set to 92% in this embodiment.

[0266] Table 1. Electrode rebound rate and bare cell thickness expansion rate of sodium secondary battery cells under different operating voltages in Example 1.

[0267] Meanwhile, the cell energy density of fully charged sodium secondary battery cells under different cutoff voltages, as well as the growth rate of battery expansion force (abbreviation of expansion force of sodium secondary battery cells, hereinafter the same) after 500 cycles, were tested, as shown in the table and Figure 9 below.

[0268] Figure 9 illustrates the changes in expansion force and voltage of the sodium secondary battery cell in Example 1 within the operating voltage range of 1.5V to 3.95V, specifically within the range of 2.0V to 3.95V, during the same charge-discharge cycle. In Figure 9, the curve pointing to the left (arrow) refers to the expansion force on the vertical axis. This curve represents the change in battery expansion force within the 2.0V to 3.95V range during the same charge-discharge cycle. For example, during the period from 0 to 250s, the expansion force of the sodium secondary battery cell first increases and then decreases as it charges; during the period from 250s to 550s, the expansion force also first increases and then decreases. The curve pointing to the right (arrow) refers to the voltage on the vertical axis. This curve represents the change in voltage within the same charge-discharge cycle, as the sodium secondary battery cell charges from 2.0V to 3.95V and then discharges from 3.95V back to 2.0V. As shown in Figure 9, during the charging process from 2.0V to 3.95V, the battery expansion force first increases and then decreases with increasing voltage.

[0269] The aforementioned trend in the positive electrode rebound rate is mainly related to the positive electrode active material. Tests revealed that, within the operating voltage range of 1.5–4.2V, the c-axis cell length of the positive electrode active material in Example 1 at 1.5V (0% SOC) was... At a voltage of 3.1V–3.3V (50%–60% SOC), the c-axis cell length is At the highest charging voltage of 4.2V (100% SOC, full charge), the c-axis cell length is The c-axis unit cell length of the positive electrode active material exhibits a characteristic of first expanding and then contracting with increasing voltage (or SOC), resulting in the positive electrode rebound rate showing the same trend. Furthermore, under the combined effect of the positive and negative electrode rebound rates, the bare cell thickness expansion rate also shows the same trend as the positive electrode rebound rate.

[0270] Therefore, based on the rebound rate or expansion rate of the positive electrode sheet and bare cell at different cutoff voltages, the width group margin of the sodium secondary battery cell can be configured as follows: that is, the width group margin of the sodium secondary battery cell at the highest charging voltage is configured to be less than or equal to the highest width group margin before reaching the highest charging voltage.

[0271] Figure 10 shows the original expansion force data for two operating voltage ranges in Example 1. When the sodium secondary battery cell is charged and discharged between 1.5V and 3.65V, the battery expansion force increases rapidly with the increase of the number of charge and discharge cycles. When the sodium secondary battery cell is charged and discharged between 1.5V and 4.0V, the battery expansion force hardly increases. To address this issue, the sodium secondary battery cell can be designed with increased width group margin and more active material placed before the electrode assembly is installed in the casing, resulting in a higher energy density for the sodium secondary battery cell.

[0272] Example 2

[0273] This embodiment provides a sodium secondary battery cell, which differs from Embodiment 1 in that its positive electrode active material is Na with a molar mass ratio of Ni, Fe, and Mn of 45.12%. 0.92 Ni 0.25 Mn 0.30 Fe 0.30 Zn 0.08 O2; at the same time, the full charge group margin of the sodium secondary battery cell in the voltage range of 1.5 to 4.0V is set to: a group margin of 92% in the width direction.

[0274] Example 3

[0275] This embodiment provides a sodium secondary battery cell, which differs from Embodiment 1 in that its positive electrode active material is Na with a molar mass ratio of Ni, Fe, and Mn of 45.55%. 0.9 Ni 0.22 Mn 0.32 Fe 0.32 Zn 0.08 O2; at the same time, the full charge group margin of the sodium secondary battery cell in the voltage range of 1.5 to 4.0V is set to: a group margin of 93% in the width direction.

[0276] Example 4

[0277] This embodiment provides a sodium secondary battery cell, which differs from Embodiment 1 in that its positive electrode active material is Na with a molar mass ratio of Ni, Fe, and Mn of 45.22%. 0.85 Ni 0.25 Mn 0.30 Fe 0.28 Cu 0.08 O2; at the same time, the full charge group margin of the sodium secondary battery cell in the voltage range of 1.5 to 4.0V is set to: a group margin of 94% in the width direction.

[0278] The sodium secondary battery cells of Examples 2 to 4 were subjected to charge-discharge tests within a voltage range of 1.5–4.0V. The charge-discharge test procedure was as follows: at 25°C, the cells were charged at a constant current rate of 0.5C to the cutoff voltage, and then charged at a constant voltage rate of 0.1C at the cutoff voltage, at which point the sodium secondary battery cell reached a fully charged state. After that, the cells were allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.5C to a voltage of 1.5V. After another 5 minutes of standing, one cycle of charge-discharge was completed. The fully charged sodium secondary battery cells were disassembled and analyzed, and their relevant performance was measured and compared with that of Example 1 under the same operating voltage. The results are shown in the table below.

[0279] Table 2. Relevant test results of sodium secondary battery cells under full charge in Examples 2 to 4

[0280] As can be seen from the analysis in Table 2, comparing Examples 1 and 2-4, the positive electrode rebound rate is similar when charged and discharged within the same operating voltage range. The width group margin of the fresh cells is designed to be 92%-95%, and the expansion force growth rate is also low, resulting in the sodium secondary battery cells exhibiting high energy density and low expansion force growth rate. In particular, energy density and low expansion force growth rate can be balanced within the 94%-95% range.

[0281] Comparative Example 1

[0282] This comparative example provides a sodium secondary battery cell, which differs from Example 1 in that the positive electrode active material is Na with a molar ratio of Ni, Fe, and Mn of 35.18%. 0.92 Ni 0.22 Mn 0.3 Fe 0.3 O4.

[0283] Comparative Example 2

[0284] This comparative example provides a sodium secondary battery cell, which differs from Example 1 in that the positive electrode active material is Na with a molar ratio of Ni, Fe, and Mn of 53.94%. 0.85 Ni 0.38 Mn 0.4 Fe 0.4 Zn 0.06 O2.

[0285] Comparative Example 3

[0286] This comparative example provides a sodium secondary battery cell, which differs from Example 1 in that: the positive electrode active material is Na with a molar ratio of Ni, Fe, and Mn of 59.53%. 0.81 Ni 0.37 Mn 0.45 Fe 0.5 O2.

[0287] Charge-discharge tests were conducted on the sodium secondary battery cells of Comparative Examples 1 to 3 within the operating voltage range of 1.5–4.0V. The charge-discharge test procedure was as follows: at 25°C, the cells were charged at a constant current rate of 0.5C to the cutoff voltage, and then charged at a constant voltage rate at the cutoff voltage until the current reached 0.1C, at which point the sodium secondary battery cell reached a fully charged state. After resting for 5 minutes, the cells were discharged at a constant current rate of 0.5C to the voltage of 1.5V, and then rested for another 5 minutes to complete one cycle of charge-discharge. The fully charged sodium secondary battery cells were disassembled and analyzed, and their relevant performance was tested. The results were compared with those of the sodium secondary battery cell of Example 1 within the same operating voltage range. The results are shown in the table below.

[0288] Table 3. Relevant test results of sodium secondary battery cells in Comparative Examples 1 to 3 under full charge.

[0289] Tests revealed that within the operating voltage range of 1.5–4.0V, the positive electrode rebound rate, negative electrode rebound rate, and bare cell thickness expansion rate of Comparative Examples 1–3 all increased with increasing voltage, reaching their highest values ​​at full charge. The positive electrode rebound rate (7.2%–9.3%) and bare cell thickness expansion rate (4.67%–5.36%) at full charge were significantly higher than those of Example 1 (positive electrode rebound rate 2.10%, bare cell thickness expansion rate 3.07%) under the same operating voltage range. Compared to Example 1, this is mainly due to the molar proportions of Ni, Fe, and Mn elements in the positive electrode active material being either too small or too large, causing the positive electrode active material to exhibit a monotonic increase in c-axis cell length during charging, rather than the characteristic of first increasing and then decreasing. Simultaneously, at the same cutoff voltage, the cell energy density of Comparative Examples 1–3 was significantly lower than that of Example 1, while the battery expansion force was significantly higher.

[0290] Based on the above embodiments and comparative examples, it can be seen that by specifically setting the width group margin of the sodium secondary battery cell—that is, setting the width group margin at the highest charging voltage to be less than or equal to the highest width group margin before reaching the highest charging voltage—and before reaching the full charge state at the highest charging voltage, the maximum width group margin before full charge can be set to the largest possible value while ensuring safety, thereby allowing as much electrode active material as possible to be placed in the casing of the sodium secondary battery cell, thus improving the energy density of the sodium secondary battery cell. Furthermore, by using electrode active materials with specific cell properties (such as positive electrode active materials), the positive electrode rebound rate and bare cell thickness expansion rate of the sodium secondary battery cell first increase and then decrease with increasing voltage or SOC during charging and discharging, which helps to achieve the aforementioned width group margin configuration and is beneficial for simultaneously obtaining high energy density and low expansion force.

[0291] Appendix:

[0292] The test methods for the relevant performance in Tables 1 to 3 are as follows:

[0293] (1) Positive electrode rebound rate, negative electrode rebound rate

[0294] At 25°C, multiple sodium secondary battery cells of the same specification were taken, and one of the sodium secondary battery cells was disassembled to obtain the initial electrode thickness (positive or negative electrode). The other sodium secondary battery cells of the same specification were charged with different dielectric voltage ranges (charging conditions refer to the above embodiment section). After full charging, the sodium secondary battery cells were disassembled, and the thickness of the electrode portion corresponding to the first wall was measured with a micrometer to obtain the electrode thickness after charging. The electrode rebound rate was calculated according to the formula: (electrode thickness after charging - initial electrode thickness) / initial electrode thickness * 100%.

[0295] (2) Bare cell thickness expansion rate

[0296] Before charging at 25℃, the sodium secondary battery cells were scanned along their height direction using a nanoVoxel-5000 CT system to obtain tomographic images of the bare cells. The maximum dimension of the bare cells in the width direction of the sodium secondary battery cells was measured to obtain the initial bare cell thickness. The sodium secondary battery cells were then charged, and the cells were analyzed after full charging at different cutoff voltages. The bare cell thickness was calculated using the formula: Bare Cell Thickness Expansion Rate = (Bare Cell Thickness After Charging - Initial Bare Cell Thickness) / Initial Bare Cell Thickness * 100%.

[0297] (3) Width direction group margin

[0298] At 25℃, the sodium secondary battery cell was scanned along its height direction using a nanoVoxel-5000 CT system to obtain tomographic images. On these images, the maximum dimension (maximum thickness of the bare cell) W1 of the electrode assembly in the width direction of the sodium secondary battery cell was measured, and the dimension W3 of the inner surface of the second wall in the width direction was also measured. The width group margin was calculated using the formula: W1 / W3*100%. For measurements of the width group margin at different charging states, the sodium secondary battery cell was charged to the corresponding voltage according to the charging conditions, charging was stopped, and a CT scan was performed on the cell to obtain W1 and W3, from which the width group margin was calculated.

[0299] (4) Cell mass energy density

[0300] At 25℃, charge at a constant current of 0.5C to the cutoff voltage, then charge at a constant voltage at the cutoff voltage until the current is 0.1C; then let stand for 5 minutes, discharge at a constant current of 0.5C to the voltage of 1.5V, and let stand for another 5 minutes. Record the discharge energy at this time.

[0301] The sodium secondary battery cells were weighed using an electronic balance.

[0302] Mass energy density (Wh / kg) = Battery energy (mAh) × Voltage (V) / Battery mass (kg).

[0303] (5) Battery expansion force growth rate

[0304] At 25℃, a sodium secondary battery cell is placed between two parallel steel plates. The distance between the two steel plates is adjusted so that each plate contacts one of the two first walls of the sodium secondary battery cell. A pressure sensor is installed between one steel plate and its corresponding first wall. The cell is charged at a constant current rate of 0.5C to the cutoff voltage, and then charged at a constant voltage rate at the cutoff voltage until the current reaches 0.05C, at which point the sodium secondary battery cell is fully charged. After resting for 5 minutes, it is discharged at a constant current rate of 0.5C until the voltage reaches 1.5V, and then rested for another 5 minutes, completing one charge-discharge cycle. The initial expansion force of the sodium secondary battery cell before charging and the expansion force after charging are obtained using the pressure sensor. The battery expansion force growth rate is calculated as (expansion force after charging - initial expansion force) / initial expansion force * 100%.

[0305] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized by, The battery cell comprises: a shell comprising two first walls oppositely arranged along a first direction; an electrode assembly arranged in the shell, the electrode assembly being located between the two first walls, and a thickness direction of the electrode assembly being parallel to the first direction; The electrode assembly includes a positive electrode tab, the positive electrode tab comprising a positive active material; the positive active material is a nickel-manganese-iron-based sodium-containing oxide, the chemical general formula of the nickel-manganese-iron-based sodium-containing oxide is Na q Ni x Mn y Fe z M p O2, wherein 0 x+y+z+p≤1, the total mass percentage of the three elements of Ni, Mn and Fe is 40%-50%; a lower limit of a use voltage of the battery cell is 1.5V-2.0V, an upper limit of the use voltage of the battery cell is 3.7V-4.2V, and a ratio of a maximum thickness of the electrode assembly under a full charge state of the battery cell to a thickness of the first wall is 16-165.

2. The battery cell of claim 1, wherein, The ratio of the maximum thickness of the electrode assembly under the full charge state of the battery cell to the thickness of the first wall is 55-75.

3. The battery cell of claim 1, wherein, The maximum thickness of the electrode assembly under the full charge state of the battery cell is 20mm-80mm.

4. The battery cell of claim 1, wherein, The shell is an aluminum shell, a Young's modulus of the shell is 65Gpa-70Gpa, and the thickness of the first wall is 0.4mm-1.2mm.

5. The battery cell of claim 4, wherein, The thickness of the first wall is 0.4mm-0.9mm.

6. The battery cell of claim 1, wherein, The shell is a steel shell, a Young's modulus of the shell is 180Gpa-190GPa, and the thickness of the first wall is 0.3mm-0.9mm.

7. The battery cell of claim 6, wherein, The thickness of the first wall is 0.3mm-0.7mm.

8. The battery cell of claim 1, wherein, The shell is an aluminum plastic film, a Young's modulus of the shell is 70Gpa-80Gpa, and the thickness of the first wall is 100μm-300μm.

9. The battery cell according to claim 1, wherein the shell is an aluminum shell, and the electrode assembly comprises a negative electrode tab; the battery cell further comprises a negative electrode lead-out portion arranged in the shell, the negative electrode lead-out portion being used for electrically connecting the negative electrode tab and a conductor outside the battery cell; a constituent material of the negative electrode lead-out portion comprises an aluminum element, and a mass percentage of the aluminum element is greater than mass percentages of other elements.

10. The battery cell of any one of claims 1 to 9, wherein, The chemical formula of the sodium-containing oxide of the nickel-manganese-iron-based satisfies 0.1≤x≤0.

5.

11. The battery cell of any one of claims 1 to 10, wherein, The chemical formula of the sodium-containing oxide of the nickel-manganese-iron-based satisfies 0.1≤y≤0.

5.

12. The battery cell of any one of claims 1 to 11, wherein, The chemical formula of the sodium-containing oxide of the nickel-manganese-iron-based satisfies 0.1≤z≤0.

5.

13. The battery cell of any one of claims 1 to 11, wherein, The chemical formula of the sodium-containing oxide of the nickel-manganese-iron-based satisfies 0.2≤z≤0.

3.

14. The battery cell of any one of claims 1 to 13, wherein, The chemical formula of the sodium-containing oxide of the nickel-manganese-iron-based satisfies 0.8≤x+y+z≤1.

15. The battery cell of any one of claims 1 to 14, wherein, The electrode assembly comprises a negative electrode tab, the negative electrode tab comprises a negative electrode active material, and a porosity of the negative electrode active material is 40%-70%.

16. The battery cell of any one of claims 1 to 15, wherein, The electrode assembly comprises a negative electrode tab, the negative electrode tab comprises a negative electrode active material, and an average pore size of the negative electrode active material is 1nm-30nm.

17. The battery cell of any one of claims 1 to 16, wherein, The electrode assembly comprises a negative electrode tab, the negative electrode tab comprises a negative electrode active material, and the negative electrode active material comprises hard carbon.

18. A battery, characterized by The battery cell comprises: a shell comprising two first walls oppositely arranged along a first direction; an electrode assembly arranged in the shell, the electrode assembly being located between the two first walls, and a thickness direction of the electrode assembly being parallel to the first direction; a lower limit of a use voltage of the battery cell is 1.5V-2.0V, an upper limit of the use voltage of the battery cell is 3.7V-4.2V, and a ratio of a maximum thickness of the electrode assembly under a full charge state of the battery cell to a thickness of the first wall is 16-165. The ratio of the maximum thickness of the electrode assembly under the full charge state of the battery cell to the thickness of the first wall is 55-75. The maximum thickness of the electrode assembly under the full charge state of the battery cell is 20mm-80mm. The shell is an aluminum shell, a Young's modulus of the shell is 65Gpa-70Gpa, and the thickness of the first wall is 0.4mm-1.2mm. The thickness of the first wall is 0.4mm-0.9mm. The shell is a steel shell, a Young's modulus of the shell is 180Gpa-190GPa, and the thickness of the first wall is 0.3mm-0.9mm. The thickness of the first wall is 0.3mm-0.7mm. The shell is an aluminum plastic film, a Young's modulus of the shell is 70Gpa-80Gpa, and the thickness of the first wall is 100μm-300μm.

9. The battery cell according to claim 1, wherein the shell is an aluminum shell, and the electrode assembly comprises a negative electrode tab; the battery cell further comprises a negative electrode lead-out portion arranged in the shell, the negative electrode lead-out portion being used for electrically connecting the negative electrode tab and a conductor outside the battery cell; a constituent material of the negative electrode lead-out portion comprises an aluminum element, and a mass percentage of the aluminum element is greater than mass percentages of other elements. The chemical formula of the sodium-containing oxide of the nickel-manganese-iron-based satisfies 0.1≤x≤0.

5. The chemical formula of the sodium-containing oxide of the nickel-manganese-iron-based satisfies 0.1≤y≤0.

5. The chemical formula of the sodium-containing oxide of the nickel-manganese-iron-based satisfies 0.1≤z≤0.

5. The chemical formula of the sodium-containing oxide of the nickel-manganese-iron-based satisfies 0.2≤z≤0.

3. The chemical formula of the sodium-containing oxide of the nickel-manganese-iron-based satisfies 0.8≤x+y+z≤1. The electrode assembly comprises a negative electrode tab, the negative electrode tab comprises a negative electrode active material, and a porosity of the negative electrode active material is 40%-70%. The electrode assembly comprises a negative electrode tab, the negative electrode tab comprises a negative electrode active material, and an average pore size of the negative electrode active material is 1nm-30nm. The electrode assembly comprises a negative electrode tab, the negative electrode tab comprises a negative electrode active material, and the negative electrode active material comprises hard carbon. The battery cell comprises: a shell comprising two first walls oppositely arranged along a first direction; an electrode assembly arranged in the shell, the electrode assembly being located between the two first walls, and a thickness direction of the electrode assembly being parallel to the first direction; a lower limit of a use voltage of the battery cell is 1.5V-2.0V, an upper limit of the use voltage of the battery cell is 3.7V-4.2V, and a ratio of a maximum thickness of the electrode assembly under a full charge state of the battery cell to a thickness of the first wall is 16-165. The ratio of the maximum thickness of the electrode assembly under the full charge state of the battery cell to the thickness of the first wall is 55-75. The maximum thickness of the electrode assembly under the full charge state of the battery cell is 20mm-80mm. The shell is an aluminum shell, a Young's modulus of the shell is 65Gpa-70Gpa, and the thickness of the first wall is 0.4mm-1.2mm. The thickness of the first wall is 0.4mm-0.9mm. The shell is a steel shell, a Young's modulus of the shell is 180Gpa-190GPa, and the thickness of the first wall is 0.3mm-0.9mm. The thickness of the first wall is 0.3mm-0.7mm. The shell is an aluminum plastic film, a Young's modulus of the shell is 70Gpa-80Gpa, and the thickness of the first wall is 100μm-300μm.

19. The battery of claim 18, wherein the battery is a lithium ion battery. The material of the end plate is aluminum alloy, and the Young's modulus of the end plate is 60-70 GPa.

20. The battery of claim 18 or 19, wherein, The thickness direction of the end plate is parallel to the first direction, and the thickness of the end plate is 20-35 mm.

21. The battery of any one of claims 18-20, wherein, The battery further comprises a busbar member, and two adjacent battery monomers are connected through the busbar member.

22. The battery of any one of claims 18-21, wherein, The battery further comprises a box, and the battery monomer group is arranged in the box and bonded to the bottom wall of the box.

23. The battery of claim 22, wherein the battery is a lithium ion battery. The battery further comprises a binding member, and the binding member is sleeved on the two end plates and the battery monomer group to fix the two end plates and the battery monomer group.

24. The battery of claim 23, wherein the cathode comprises a lithium metal oxide. The binding member comprises a first binding member, and the first binding member is a steel belt or a plastic belt.

25. The battery of claim 23, wherein the cathode comprises a lithium metal oxide. The binding member comprises a first binding member, and the number of the first binding member is two, and the two first binding members are arranged at intervals in a second direction, and the second direction is parallel to the thickness direction of the bottom wall.

26. The battery of claim 23, wherein the cathode comprises a lithium metal oxide. The binding member comprises a first binding member and a second binding member, and the first binding member and the second binding member are arranged at intervals in a second direction, and the second direction is parallel to the thickness direction of the bottom wall.

27. The battery of claim 26, wherein the battery is a lithium ion battery. The first binding member is away from the bottom wall relative to the second binding member, and the strength of the first binding member is greater than that of the second binding member.

28. An electrical device, comprising: The first binding member is a steel belt, and the second binding member is a plastic belt. The battery monomer comprises any one of claims 1-17, or the battery comprises any one of claims 18-27.

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